Balance systems are used to develop trim balance information for rotating equipments and assemblies. These balance systems determine the unbalance of rotating equipments relative to a given point location on the rotating element, generally identified by a tach signal, and also determine the amplitude of the unbalance. With this information, it is then possible to place weights on the equipment opposite the unbalance to balance the rotating member. The information desired is revolutions per minute, the exact location of the unbalance, and the amount of weight required for balancing.
The tachometers used provide normal tachometer signals and the vibration data signal pickups are known vibration signal generators. In known systems for making such trim balance information determinations, the vibration or displacement data signal is fed through a tracking filter through which the amplitude or displacement of the signal is determined. A sine wave is generated that is frequency and phase coherent with the tachometer signal. Then a phase comparison is made of the fundamental of the vibration data signal relative to the tachometer signal that establishes the phase displacement of the unbalance, and thus its location.
In the present system for determining balance information, the vibration data signal is nulled by successive automatic adjustments of the phase of a synthesized sine wave relative to the tachometer signal, thus providing an automatic means for bracketing the fundamental of the input vibration unbalance signal through successive bracketing adjustments of the phase of the synthesized sine wave. This provides automatic and positive locating of the phase displacement of the input data signal and thus the desired phase displacement and location of the unbalance.